Peptide Biologic Markers are proving valuable in long term follow-up of cancer patients and for assessing results of anticancer therapy. We propose to investigate the feasibility of using serum and/or cerebrospinal fluid isoenzyme components as biologic markers as an indication of presence or absence of tumor and response to treatment. The rationale is based on the knowledge that tumors tend to produce fetal isoenzymes and that serum levels of many enzymes reflect tumor mass rather than spread to specific metastic sites. We hope that a profile of isoenzyme tests can be developed that will be economically feasible and applicable to a larger proportion of cancer patients than the current group now suitable for follow-up using CEA and alpha-fetoprotein or hormone products of tumors. Enzymes proposed for initial investigation include Aldolase, Lactate Dehydrogenase, Malate Dehydrogenase, Glucose-ATP-Phosphotransferases, Phosphorylase, Leucine Aminotransferase and Adenylate kinase. The starch gel and disc gel electrophoretic techniques will be used. These methods have the advantage of high resolution and require small samples so that a number of isoenzyme studies can conveniently be done. Results will be correlated with clinical data such as recurrence of disease and response to chemotherapy. This study should indicate which isoenzyme changes, if any, signal recurrence of disease or response to therapy. A profile analysis should increase the accuracy of such measurements by being constructed in such a manner that changes caused by isolated organ failure will be discounted.